Combined seat and backrest unit for a chair



FIG. 1 is a front elevational view of a combined seat and backrest unit for a chair showing my design;

FIG. 2 is a left side elevational view;

FIG. 3 is a rear elevational view;

FIG. 4 is a front perspective view;

FIG. 5 is a bottom plan view; and

FIG. 6 is a top plan view thereof.

The side of the chair not shown is a mirror image of the side shown in FIG. 2. 

The ornamental design for a combined seat and backrest unit for a chair, as shown and described. 